In order to ensure heat preservation of aluminum alloy wheel molds during a die casting process and successful removal of die castings from a mold, the mold typically needs to be uniformly sprayed with a layer of paint on inner walls thereof before being heated and put on the machine. At present, molds are manually sprayed using a handheld spray gun in all the wheel manufacturers. Use of this spraying mode not only makes it very difficult to attain a uniform and consistent spraying thickness, but also causes tremendous damages to human body due to operating environments. This device can adjust different spraying parameters according to different wheel types and is thus high in degree of automation.